1. Technical Field
The present invention relates to a liquid ejecting head such as an ink jet type recording head, and more particularly, to a liquid ejecting head which introduces a liquid stored in a liquid storage member into a pressure chamber through a liquid introducing portion such as a liquid introducing needle, and discharges the liquid introduced into the pressure chamber from nozzles as liquid droplets.
2. Related Art
A liquid ejecting head is, for example, an ink jet type recording head for an image recording apparatus such as an ink jet type recording apparatus (hereinafter, simply referred to as a recording head). However, the liquid ejecting head has been applied to various kinds of manufacturing apparatuses taking an advantage of being able to land very small amounts of liquid precisely onto a designated position. For example, it is applied to a display manufacturing apparatus used for manufacturing a color filter for a liquid crystal display, or the like, an electrode forming apparatus used for forming an electrode for an organic electro luminescence (EL) display, a field emission display (FED), or the like, and a chip manufacturing apparatus used for manufacturing a biochip (biochemical device). A recording head for an image recording apparatus ejects liquid-phase ink, and a color material ejecting head for a display manufacturing apparatus ejects solutions of color materials of R (Red), G (Green), B (Blue). Additionally, an electrode material ejecting head for an electrode forming apparatus ejects liquid-phase electrode materials, and a bio-organic substance ejecting head for a chip manufacturing apparatus ejects solutions of a bio-organic substance.
In the above-mentioned recording head, for example, an ink introducing needle which is a kind of liquid introducing needle is inserted into an ink cartridge as a liquid storage member having liquid-phase ink enclosed therein. Accordingly, the ink stored in the ink cartridge is introduced from the ink introducing needle to a pressure chamber side through a ink flow passage in the recording head. A pressure variation is generated in the pressure chamber by driving of a pressure generating unit, and the pressure variation is used to eject (discharge) the ink from nozzles as liquid droplets.
In the above-mentioned recording head, however, when connecting the ink cartridge to the ink introducing needle, bubbles could be mixed in and flow to the ink introducing needle. If the bubbles are entrained into the pressure chamber side through the ink flow passage, there is concern that defects could be caused, such as pressure loss which is caused by the bubbles absorbing the pressure variation which is generated at a recording operation (an ink droplet ejecting operation), or insufficient ink supply which is caused by the bubbles blocking the flow passage.
To solve these problems, it has been proposed that a bubble chamber 72 which communicates with a bottom end of an introducing flow passage 71 on an upstream side, and a filter 73 which is provided at the bottom of the bubble chamber are included in an ink introducing needle 70, as shown in FIGS. 6A to 6C (for example, see JP-A-2009-006730). Therefore, it is possible that the ink flowing from the upstream side to the downstream side is filtrated by the filter 73, whereby the bubbles B entrained in the ink are accommodated in the bubble chamber 72. As a result, the bubbles B are not permitted to flow to a downstream side at the recording operation. Also, the bubbles B accommodated in the bubble chamber 72 are discharged compulsively by a cleaning operation. Specifically, a flow rate of the ink in the ink introducing needle 70 is set to be greater than that in the recording operation, whereby a greater pressure difference is generated between the upstream side and the downstream side comparing to that in the recording operation. Accordingly, the bubbles B in the bubble chamber 72 are compulsively sent to the downstream side through the filter and then discharged from the nozzles with the ink, as shown in FIG. 6B.
A filter 73 with a lyophilic property (a contact angle θ of the ink with respect to the filter 73 is less than 90°) is used as the above-mentioned filter 73, so as to not permit a flow of the ink passing the filter 73 from being disturbed by the bubbles B covering a surface of the filter 73 at the recording operation. However, in such a filter 73, a contact size between the bubble B and the filter 73 becomes small at the cleaning operation, as shown in FIG. 6B. That is, the ink goes around and cuts in between the bubble B and the filter 73, and then the ink flows downward with avoiding the bubble B. As a result, there is a liability that the bubbles B are discharged insufficiently during the cleaning operation, and the large bubbles B remain in the bubble chamber 72, as shown in FIG. 6C. If the large bubbles B remain in the bubble chamber 72, there is concern that the bubbles B flow into the pressure chamber side erroneously or a flow of the ink toward the pressure chamber side is disturbed during the recording operation.